Problems with hadronicηcdecays and the perturbative QCD scheme for exclusive reactions

We consider some observed decays of the ${\eta }_c$ which should be forbidden in the perturbative QCD description of exclusive reactions: ${\eta }_c\to \rho \rho$, $K^{*}{\overline{K}}^{*}$, $\phi \phi$. It is shown explicitly that quark mass corrections do not help and still give a zero result. Also the experimental value for the decay rate $\Gamma ({\eta }_c\to p\overline{p})$ is argued to be anomalously large. Implications for the perturbative QCD scheme are discussed, and some other possible explanations of the data are suggested.